Technical Field
The present disclosure relates to a medical solution administration device. For example, the present disclosure is suitable for applying to a case where insulin is administered in a body.
Background Art
A so-called syringe pump type medical solution administration device has been conventionally proposed (for example, refer to JP 2010-501283 W) as a device for administering medical solution (insulin). The syringe pump type medical solution administration device is a portable device used by being stuck to skin of a user, and it administers the medical solution filled in an external cylinder to a body by pushing out the medical solution via a plunger.
A medical solution can be supplied into the body by a so-called piston pump type supply unit in the medical solution administration device. In the medical solution administration device using the piston pump type supply unit, a seal such as an O-ring and an X-ring is provided on an outer circumference of a piston sliding in a cylinder. This prevents the medical solution from leaking outside the device from between the cylinder and the piston.
Here, as illustrated in FIGS. 1 and 2, a starting resistance between sliding parts of the piston and the seal increases with time. After the lapse of a predetermined time, the increase in the starting resistance becomes gradual, and the value tends to be a constant value. This is considered because the seal gradually enters a recess on a sliding surface of the piston with time. FIG. 1 is a diagram of changes of the starting resistances of a plurality of kinds of seals caused by elapse of time. FIG. 2 is a diagram of an experiment result indicating changes of thrusts (starting resistance) in a case where the piston is started by using the piston having a diameter of 1.03 mm and the X-ring after different leaving times (0, 24, 72, and 96 hours) have elapsed.
Therefore, in this medical solution administration device, because the starting resistance between the piston and the seal is large, it is necessary to use a large force to start the piston to overcome the starting resistance at the time of starting the use of it.
On the other hand, it is desired that the portable medical solution administration device be reduced in size because the device is used by being stuck to the skin of the user.